I've always been amazed at the variety of stem lengths offered for/employed on serious cycles..
Cinelli made classic stems in lengths from 7cm to 14cm -- a difference of nearly a huge 2.5 inches! I've no idea what gives today -- probably more choice.
It seems to this physical science ignoramus that stem length has a direct & immediate bearing on steering and handling, in combo with fork rake (which varies relatively slightly) and head tube angle (which also varies to the tune of not more than 3 degrees on classic racing frames).
So what's up? Isn't there a rather narrow window of optimum stem length for ideal steering/handling? Why does it seem that stem length is employed as a quick & dirty solution to inappropriate top tube length, arather than it being a crucial consideration for optimum control of the bicycle?